The prototypes are being built for the Army’s Joint Multi-Role Technology Demonstrator project by Bell Helicopter and the competing Sikorsky-Boeing team.

Bell is building the V-280 Valor, a tiltrotor aircraft that can take off and land like a helicopter, or rotate its propellers to fly fast like a fixed-wing plane. Sikorsky and Boeing are building the SB-1 Defiant, a high-speed coaxial helicopter with one rotor mounted atop the other. Bell officials say V-280 ground testing is scheduled for next April and first flight for September 2017; Sikorsky-Boeing reps said their SB-1 would fly next year as well.

The project will feed into the Future Vertical Lift program, a vast effort to replace all Army helicopters — which include the AH-64 Apache, CH-46 Chinook, and the OH-58 Kiowa — at a projected cost of around $100 billion.

The US Army isn’t planning to buy its first new rotorcraft until after 2030. That’s because its acquisition budget — aircraft, armored vehicles, and so forth — has taken a major hit.